--- /dev/null
+ PXA-Camera Host Driver
+ ======================
+
+Constraints
+-----------
+ a) Image size for YUV422P format
+ All YUV422P images are enforced to have width x height % 16 = 0.
+ This is due to DMA constraints, which transfers only planes of 8 byte
+ multiples.
+
+
+Global video workflow
+---------------------
+ a) QCI stopped
+ Initialy, the QCI interface is stopped.
+ When a buffer is queued (pxa_videobuf_ops->buf_queue), the QCI starts.
+
+ b) QCI started
+ More buffers can be queued while the QCI is started without halting the
+ capture. The new buffers are "appended" at the tail of the DMA chain, and
+ smoothly captured one frame after the other.
+
+ Once a buffer is filled in the QCI interface, it is marked as "DONE" and
+ removed from the active buffers list. It can be then requeud or dequeued by
+ userland application.
+
+ Once the last buffer is filled in, the QCI interface stops.
+
+
+DMA usage
+---------
+ a) DMA flow
+ - first buffer queued for capture
+ Once a first buffer is queued for capture, the QCI is started, but data
+ transfer is not started. On "End Of Frame" interrupt, the irq handler
+ starts the DMA chain.
+ - capture of one videobuffer
+ The DMA chain starts transfering data into videobuffer RAM pages.
+ When all pages are transfered, the DMA irq is raised on "ENDINTR" status
+ - finishing one videobuffer
+ The DMA irq handler marks the videobuffer as "done", and removes it from
+ the active running queue
+ Meanwhile, the next videobuffer (if there is one), is transfered by DMA
+ - finishing the last videobuffer
+ On the DMA irq of the last videobuffer, the QCI is stopped.
+
+ b) DMA prepared buffer will have this structure
+
+ +------------+-----+---------------+-----------------+
+ | desc-sg[0] | ... | desc-sg[last] | finisher/linker |
+ +------------+-----+---------------+-----------------+
+
+ This structure is pointed by dma->sg_cpu.
+ The descriptors are used as follows :
+ - desc-sg[i]: i-th descriptor, transfering the i-th sg
+ element to the video buffer scatter gather
+ - finisher: has ddadr=DADDR_STOP, dcmd=ENDIRQEN
+ - linker: has ddadr= desc-sg[0] of next video buffer, dcmd=0
+
+ For the next schema, let's assume d0=desc-sg[0] .. dN=desc-sg[N],
+ "f" stands for finisher and "l" for linker.
+ A typical running chain is :
+
+ Videobuffer 1 Videobuffer 2
+ +---------+----+---+ +----+----+----+---+
+ | d0 | .. | dN | l | | d0 | .. | dN | f |
+ +---------+----+-|-+ ^----+----+----+---+
+ | |
+ +----+
+
+ After the chaining is finished, the chain looks like :
+
+ Videobuffer 1 Videobuffer 2 Videobuffer 3
+ +---------+----+---+ +----+----+----+---+ +----+----+----+---+
+ | d0 | .. | dN | l | | d0 | .. | dN | l | | d0 | .. | dN | f |
+ +---------+----+-|-+ ^----+----+----+-|-+ ^----+----+----+---+
+ | | | |
+ +----+ +----+
+ new_link
+
+ c) DMA hot chaining timeslice issue
+
+ As DMA chaining is done while DMA _is_ running, the linking may be done
+ while the DMA jumps from one Videobuffer to another. On the schema, that
+ would be a problem if the following sequence is encountered :
+
+ - DMA chain is Videobuffer1 + Videobuffer2
+ - pxa_videobuf_queue() is called to queue Videobuffer3
+ - DMA controller finishes Videobuffer2, and DMA stops
+ =>
+ Videobuffer 1 Videobuffer 2
+ +---------+----+---+ +----+----+----+---+
+ | d0 | .. | dN | l | | d0 | .. | dN | f |
+ +---------+----+-|-+ ^----+----+----+-^-+
+ | | |
+ +----+ +-- DMA DDADR loads DDADR_STOP
+
+ - pxa_dma_add_tail_buf() is called, the Videobuffer2 "finisher" is
+ replaced by a "linker" to Videobuffer3 (creation of new_link)
+ - pxa_videobuf_queue() finishes
+ - the DMA irq handler is called, which terminates Videobuffer2
+ - Videobuffer3 capture is not scheduled on DMA chain (as it stopped !!!)
+
+ Videobuffer 1 Videobuffer 2 Videobuffer 3
+ +---------+----+---+ +----+----+----+---+ +----+----+----+---+
+ | d0 | .. | dN | l | | d0 | .. | dN | l | | d0 | .. | dN | f |
+ +---------+----+-|-+ ^----+----+----+-|-+ ^----+----+----+---+
+ | | | |
+ +----+ +----+
+ new_link
+ DMA DDADR still is DDADR_STOP
+
+ - pxa_camera_check_link_miss() is called
+ This checks if the DMA is finished and a buffer is still on the
+ pcdev->capture list. If that's the case, the capture will be restarted,
+ and Videobuffer3 is scheduled on DMA chain.
+ - the DMA irq handler finishes
+
+ Note: if DMA stops just after pxa_camera_check_link_miss() reads DDADR()
+ value, we have the guarantee that the DMA irq handler will be called back
+ when the DMA will finish the buffer, and pxa_camera_check_link_miss() will
+ be called again, to reschedule Videobuffer3.
+
+--
+Author: Robert Jarzmik <robert.jarzmik@free.fr>
pxa_dma->sg_cpu[i].dtadr = sg_dma_address(sg) + offset;
pxa_dma->sg_cpu[i].dcmd =
DCMD_FLOWSRC | DCMD_BURST8 | DCMD_INCTRGADDR | xfer_len;
+#ifdef DEBUG
+ if (!i)
+ pxa_dma->sg_cpu[i].dcmd |= DCMD_STARTIRQEN;
+#endif
pxa_dma->sg_cpu[i].ddadr =
pxa_dma->sg_dma + (i + 1) * sizeof(struct pxa_dma_desc);
break;
}
- pxa_dma->sg_cpu[sglen - 1].ddadr = DDADR_STOP;
- pxa_dma->sg_cpu[sglen - 1].dcmd |= DCMD_ENDIRQEN;
+ pxa_dma->sg_cpu[sglen].ddadr = DDADR_STOP;
+ pxa_dma->sg_cpu[sglen].dcmd = DCMD_FLOWSRC | DCMD_BURST8 | DCMD_ENDIRQEN;
/*
* Handle 1 special case :
return 0;
}
+static void pxa_videobuf_set_actdma(struct pxa_camera_dev *pcdev,
+ struct pxa_buffer *buf)
+{
+ buf->active_dma = DMA_Y;
+ if (pcdev->channels == 3)
+ buf->active_dma |= DMA_U | DMA_V;
+}
+
+/*
+ * Please check the DMA prepared buffer structure in :
+ * Documentation/video4linux/pxa_camera.txt
+ * Please check also in pxa_camera_check_link_miss() to understand why DMA chain
+ * modification while DMA chain is running will work anyway.
+ */
static int pxa_videobuf_prepare(struct videobuf_queue *vq,
struct videobuf_buffer *vb, enum v4l2_field field)
{
}
buf->inwork = 0;
- buf->active_dma = DMA_Y;
- if (pcdev->channels == 3)
- buf->active_dma |= DMA_U | DMA_V;
+ pxa_videobuf_set_actdma(pcdev, buf);
return 0;
return ret;
}
+/**
+ * pxa_dma_start_channels - start DMA channel for active buffer
+ * @pcdev: pxa camera device
+ *
+ * Initialize DMA channels to the beginning of the active video buffer, and
+ * start these channels.
+ */
+static void pxa_dma_start_channels(struct pxa_camera_dev *pcdev)
+{
+ int i;
+ struct pxa_buffer *active;
+
+ active = pcdev->active;
+
+ for (i = 0; i < pcdev->channels; i++) {
+ dev_dbg(pcdev->dev, "%s (channel=%d) ddadr=%08x\n", __func__,
+ i, active->dmas[i].sg_dma);
+ DDADR(pcdev->dma_chans[i]) = active->dmas[i].sg_dma;
+ DCSR(pcdev->dma_chans[i]) = DCSR_RUN;
+ }
+}
+
+static void pxa_dma_stop_channels(struct pxa_camera_dev *pcdev)
+{
+ int i;
+
+ for (i = 0; i < pcdev->channels; i++) {
+ dev_dbg(pcdev->dev, "%s (channel=%d)\n", __func__, i);
+ DCSR(pcdev->dma_chans[i]) = 0;
+ }
+}
+
+static void pxa_dma_update_sg_tail(struct pxa_camera_dev *pcdev,
+ struct pxa_buffer *buf)
+{
+ int i;
+
+ for (i = 0; i < pcdev->channels; i++)
+ pcdev->sg_tail[i] = buf->dmas[i].sg_cpu + buf->dmas[i].sglen;
+}
+
+static void pxa_dma_add_tail_buf(struct pxa_camera_dev *pcdev,
+ struct pxa_buffer *buf)
+{
+ int i;
+ struct pxa_dma_desc *buf_last_desc;
+
+ for (i = 0; i < pcdev->channels; i++) {
+ buf_last_desc = buf->dmas[i].sg_cpu + buf->dmas[i].sglen;
+ buf_last_desc->ddadr = DDADR_STOP;
+
+ if (!pcdev->sg_tail[i])
+ continue;
+ pcdev->sg_tail[i]->ddadr = buf->dmas[i].sg_dma;
+ }
+
+ pxa_dma_update_sg_tail(pcdev, buf);
+}
+
+/**
+ * pxa_camera_start_capture - start video capturing
+ * @pcdev: camera device
+ *
+ * Launch capturing. DMA channels should not be active yet. They should get
+ * activated at the end of frame interrupt, to capture only whole frames, and
+ * never begin the capture of a partial frame.
+ */
+static void pxa_camera_start_capture(struct pxa_camera_dev *pcdev)
+{
+ unsigned long cicr0, cifr;
+
+ dev_dbg(pcdev->dev, "%s\n", __func__);
+ /* Reset the FIFOs */
+ cifr = __raw_readl(pcdev->base + CIFR) | CIFR_RESET_F;
+ __raw_writel(cifr, pcdev->base + CIFR);
+ /* Enable End-Of-Frame Interrupt */
+ cicr0 = __raw_readl(pcdev->base + CICR0) | CICR0_ENB;
+ cicr0 &= ~CICR0_EOFM;
+ __raw_writel(cicr0, pcdev->base + CICR0);
+}
+
+static void pxa_camera_stop_capture(struct pxa_camera_dev *pcdev)
+{
+ unsigned long cicr0;
+
+ pxa_dma_stop_channels(pcdev);
+
+ cicr0 = __raw_readl(pcdev->base + CICR0) & ~CICR0_ENB;
+ __raw_writel(cicr0, pcdev->base + CICR0);
+
+ dev_dbg(pcdev->dev, "%s\n", __func__);
+}
+
static void pxa_videobuf_queue(struct videobuf_queue *vq,
struct videobuf_buffer *vb)
{
struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
struct pxa_camera_dev *pcdev = ici->priv;
struct pxa_buffer *buf = container_of(vb, struct pxa_buffer, vb);
- struct pxa_buffer *active;
unsigned long flags;
- int i;
- dev_dbg(&icd->dev, "%s (vb=0x%p) 0x%08lx %d\n", __func__,
- vb, vb->baddr, vb->bsize);
+ dev_dbg(&icd->dev, "%s (vb=0x%p) 0x%08lx %d active=%p\n", __func__,
+ vb, vb->baddr, vb->bsize, pcdev->active);
+
spin_lock_irqsave(&pcdev->lock, flags);
list_add_tail(&vb->queue, &pcdev->capture);
vb->state = VIDEOBUF_ACTIVE;
- active = pcdev->active;
+ pxa_dma_add_tail_buf(pcdev, buf);
- if (!active) {
- unsigned long cifr, cicr0;
-
- cifr = __raw_readl(pcdev->base + CIFR) | CIFR_RESET_F;
- __raw_writel(cifr, pcdev->base + CIFR);
-
- for (i = 0; i < pcdev->channels; i++) {
- DDADR(pcdev->dma_chans[i]) = buf->dmas[i].sg_dma;
- DCSR(pcdev->dma_chans[i]) = DCSR_RUN;
- pcdev->sg_tail[i] = buf->dmas[i].sg_cpu + buf->dmas[i].sglen - 1;
- }
-
- pcdev->active = buf;
-
- cicr0 = __raw_readl(pcdev->base + CICR0) | CICR0_ENB;
- __raw_writel(cicr0, pcdev->base + CICR0);
- } else {
- struct pxa_cam_dma *buf_dma;
- struct pxa_cam_dma *act_dma;
- int nents;
-
- for (i = 0; i < pcdev->channels; i++) {
- buf_dma = &buf->dmas[i];
- act_dma = &active->dmas[i];
- nents = buf_dma->sglen;
-
- /* Stop DMA engine */
- DCSR(pcdev->dma_chans[i]) = 0;
-
- /* Add the descriptors we just initialized to
- the currently running chain */
- pcdev->sg_tail[i]->ddadr = buf_dma->sg_dma;
- pcdev->sg_tail[i] = buf_dma->sg_cpu + buf_dma->sglen - 1;
-
- /* Setup a dummy descriptor with the DMA engines current
- * state
- */
- buf_dma->sg_cpu[nents].dsadr =
- pcdev->res->start + 0x28 + i*8; /* CIBRx */
- buf_dma->sg_cpu[nents].dtadr =
- DTADR(pcdev->dma_chans[i]);
- buf_dma->sg_cpu[nents].dcmd =
- DCMD(pcdev->dma_chans[i]);
-
- if (DDADR(pcdev->dma_chans[i]) == DDADR_STOP) {
- /* The DMA engine is on the last
- descriptor, set the next descriptors
- address to the descriptors we just
- initialized */
- buf_dma->sg_cpu[nents].ddadr = buf_dma->sg_dma;
- } else {
- buf_dma->sg_cpu[nents].ddadr =
- DDADR(pcdev->dma_chans[i]);
- }
-
- /* The next descriptor is the dummy descriptor */
- DDADR(pcdev->dma_chans[i]) = buf_dma->sg_dma + nents *
- sizeof(struct pxa_dma_desc);
-
- DCSR(pcdev->dma_chans[i]) = DCSR_RUN;
- }
- }
+ if (!pcdev->active)
+ pxa_camera_start_capture(pcdev);
spin_unlock_irqrestore(&pcdev->lock, flags);
}
struct videobuf_buffer *vb,
struct pxa_buffer *buf)
{
- unsigned long cicr0;
+ int i;
/* _init is used to debug races, see comment in pxa_camera_reqbufs() */
list_del_init(&vb->queue);
do_gettimeofday(&vb->ts);
vb->field_count++;
wake_up(&vb->done);
+ dev_dbg(pcdev->dev, "%s dequeud buffer (vb=0x%p)\n", __func__, vb);
if (list_empty(&pcdev->capture)) {
+ pxa_camera_stop_capture(pcdev);
pcdev->active = NULL;
- DCSR(pcdev->dma_chans[0]) = 0;
- DCSR(pcdev->dma_chans[1]) = 0;
- DCSR(pcdev->dma_chans[2]) = 0;
-
- cicr0 = __raw_readl(pcdev->base + CICR0) & ~CICR0_ENB;
- __raw_writel(cicr0, pcdev->base + CICR0);
+ for (i = 0; i < pcdev->channels; i++)
+ pcdev->sg_tail[i] = NULL;
return;
}
struct pxa_buffer, vb.queue);
}
+/**
+ * pxa_camera_check_link_miss - check missed DMA linking
+ * @pcdev: camera device
+ *
+ * The DMA chaining is done with DMA running. This means a tiny temporal window
+ * remains, where a buffer is queued on the chain, while the chain is already
+ * stopped. This means the tailed buffer would never be transfered by DMA.
+ * This function restarts the capture for this corner case, where :
+ * - DADR() == DADDR_STOP
+ * - a videobuffer is queued on the pcdev->capture list
+ *
+ * Please check the "DMA hot chaining timeslice issue" in
+ * Documentation/video4linux/pxa_camera.txt
+ *
+ * Context: should only be called within the dma irq handler
+ */
+static void pxa_camera_check_link_miss(struct pxa_camera_dev *pcdev)
+{
+ int i, is_dma_stopped = 1;
+
+ for (i = 0; i < pcdev->channels; i++)
+ if (DDADR(pcdev->dma_chans[i]) != DDADR_STOP)
+ is_dma_stopped = 0;
+ dev_dbg(pcdev->dev, "%s : top queued buffer=%p, dma_stopped=%d\n",
+ __func__, pcdev->active, is_dma_stopped);
+ if (pcdev->active && is_dma_stopped)
+ pxa_camera_start_capture(pcdev);
+}
+
static void pxa_camera_dma_irq(int channel, struct pxa_camera_dev *pcdev,
enum pxa_camera_active_dma act_dma)
{
unsigned long flags;
u32 status, camera_status, overrun;
struct videobuf_buffer *vb;
- unsigned long cifr, cicr0;
spin_lock_irqsave(&pcdev->lock, flags);
status = DCSR(channel);
- DCSR(channel) = status | DCSR_ENDINTR;
+ DCSR(channel) = status;
+
+ camera_status = __raw_readl(pcdev->base + CISR);
+ overrun = CISR_IFO_0;
+ if (pcdev->channels == 3)
+ overrun |= CISR_IFO_1 | CISR_IFO_2;
if (status & DCSR_BUSERR) {
dev_err(pcdev->dev, "DMA Bus Error IRQ!\n");
goto out;
}
- if (!(status & DCSR_ENDINTR)) {
+ if (!(status & (DCSR_ENDINTR | DCSR_STARTINTR))) {
dev_err(pcdev->dev, "Unknown DMA IRQ source, "
"status: 0x%08x\n", status);
goto out;
goto out;
}
- camera_status = __raw_readl(pcdev->base + CISR);
- overrun = CISR_IFO_0;
- if (pcdev->channels == 3)
- overrun |= CISR_IFO_1 | CISR_IFO_2;
- if (camera_status & overrun) {
- dev_dbg(pcdev->dev, "FIFO overrun! CISR: %x\n", camera_status);
- /* Stop the Capture Interface */
- cicr0 = __raw_readl(pcdev->base + CICR0) & ~CICR0_ENB;
- __raw_writel(cicr0, pcdev->base + CICR0);
-
- /* Stop DMA */
- DCSR(channel) = 0;
- /* Reset the FIFOs */
- cifr = __raw_readl(pcdev->base + CIFR) | CIFR_RESET_F;
- __raw_writel(cifr, pcdev->base + CIFR);
- /* Enable End-Of-Frame Interrupt */
- cicr0 &= ~CICR0_EOFM;
- __raw_writel(cicr0, pcdev->base + CICR0);
- /* Restart the Capture Interface */
- __raw_writel(cicr0 | CICR0_ENB, pcdev->base + CICR0);
- goto out;
- }
-
vb = &pcdev->active->vb;
buf = container_of(vb, struct pxa_buffer, vb);
WARN_ON(buf->inwork || list_empty(&vb->queue));
- dev_dbg(pcdev->dev, "%s (vb=0x%p) 0x%08lx %d\n", __func__,
- vb, vb->baddr, vb->bsize);
- buf->active_dma &= ~act_dma;
- if (!buf->active_dma)
- pxa_camera_wakeup(pcdev, vb, buf);
+ dev_dbg(pcdev->dev, "%s channel=%d %s%s(vb=0x%p) dma.desc=%x\n",
+ __func__, channel, status & DCSR_STARTINTR ? "SOF " : "",
+ status & DCSR_ENDINTR ? "EOF " : "", vb, DDADR(channel));
+
+ if (status & DCSR_ENDINTR) {
+ if (camera_status & overrun) {
+ dev_dbg(pcdev->dev, "FIFO overrun! CISR: %x\n",
+ camera_status);
+ pxa_camera_stop_capture(pcdev);
+ pxa_camera_start_capture(pcdev);
+ goto out;
+ }
+ buf->active_dma &= ~act_dma;
+ if (!buf->active_dma) {
+ pxa_camera_wakeup(pcdev, vb, buf);
+ pxa_camera_check_link_miss(pcdev);
+ }
+ }
out:
spin_unlock_irqrestore(&pcdev->lock, flags);
{
struct pxa_camera_dev *pcdev = data;
unsigned long status, cicr0;
+ struct pxa_buffer *buf;
+ struct videobuf_buffer *vb;
status = __raw_readl(pcdev->base + CISR);
dev_dbg(pcdev->dev, "Camera interrupt status 0x%lx\n", status);
__raw_writel(status, pcdev->base + CISR);
if (status & CISR_EOF) {
- int i;
- for (i = 0; i < pcdev->channels; i++) {
- DDADR(pcdev->dma_chans[i]) =
- pcdev->active->dmas[i].sg_dma;
- DCSR(pcdev->dma_chans[i]) = DCSR_RUN;
- }
+ pcdev->active = list_first_entry(&pcdev->capture,
+ struct pxa_buffer, vb.queue);
+ vb = &pcdev->active->vb;
+ buf = container_of(vb, struct pxa_buffer, vb);
+ pxa_videobuf_set_actdma(pcdev, buf);
+
+ pxa_dma_start_channels(pcdev);
+
cicr0 = __raw_readl(pcdev->base + CICR0) | CICR0_EOFM;
__raw_writel(cicr0, pcdev->base + CICR0);
}
ret = pcdev->icd->ops->resume(pcdev->icd);
/* Restart frame capture if active buffer exists */
- if (!ret && pcdev->active) {
- unsigned long cifr, cicr0;
-
- /* Reset the FIFOs */
- cifr = __raw_readl(pcdev->base + CIFR) | CIFR_RESET_F;
- __raw_writel(cifr, pcdev->base + CIFR);
-
- cicr0 = __raw_readl(pcdev->base + CICR0);
- cicr0 &= ~CICR0_EOFM; /* Enable End-Of-Frame Interrupt */
- cicr0 |= CICR0_ENB; /* Restart the Capture Interface */
- __raw_writel(cicr0, pcdev->base + CICR0);
- }
+ if (!ret && pcdev->active)
+ pxa_camera_start_capture(pcdev);
return ret;
}
projects / linux-2.6-omap-h63xx.git / commitdiff